Many imaging applications require very sensitive light detection and wide dynamic range. An example is urban imaging where the light intensity can vary over several orders of magnitude (e.g., dark alleys to street lights). To achieve the best sensitivity, single photoelectron detection is needed, but often dynamic range is sacrificed. Several devices are available for detecting single photons (photoelectrons), such as photomultiplier tubes, intensified solid-state imagers, avalanche-register charge-coupled device (CCD) imagers, and Geiger-mode avalanche photodiodes. Each of these approaches has advantages for specific low-light-level imaging applications, but is limited in dynamic range.